Cycloolefin polymers such as norbornene polymers are valuable as insulating materials in the electronics field due to excellent dielectric properties and low water absorption properties. Of the cycloolefin polymers, cycloolefin addition polymers typified by norbornene addition polymers are generally suitable for use as various kinds of moldings, sealing materials for electronic parts, and insulating materials, owing to various properties such as low moisture-absorption and excellent dielectric properties.
Cycloolefin polymers in general and norbornene-type polymers in particular can be made using nickel catalysts. For example, U.S. Pat. No. 6,136,499 describes the use of EnNi(C6F5)2 (where n=1 or 2 and where E is a neutral electron donor ligand). Where E is toluene, such catalyst is made by the reaction of suitable starting materials such nickel(II) trifluoroacetate and C6F5MgBr (Brezinski and Klabunde in Organometallics, 1983, 2, 1116). Such nickel catalysts are made using fluorinated aryl Grignard reagents.
However, handling of fluorinated Grignard reagents raises safety concerns. There have been reports of explosions associated with fluorinated aryl magnesium halides (See, a) Appleby, Chem. Ind. (London) 1971, 4, 120, b) Moore and Waymouth, Chem. Eng. News 1997, 75(11), 6, and c) Reger, et al. Inorg. Synth. 2004, 34, 5-8).
In Organometallics, 2005, 24, 3579 the synthesis of [3,5-bis(trifluoromethyl)phenyl] magnesium bromide is described using iPrMgCl via Knochel's procedure described in Tetrahedron Letters 1999, 40, 7449. In this article it is reported: “The recent report by Leazer et al. confirms that while [3,5-bis(trifluoromethyl)phenyl] magnesium bromide is not a hazard by itself, explosive exothermic decompositions of (trifluoromethyl)aryl Grignard reagents occurs in the presence of any excess magnesium metal”. Leazer describes Knochel's procedure as “safe and reliable” and highlights that: “We found Knochel's procedure [ . . . ] to be the best method for the preparation of (trifluoromethyl)phenyl Grignard reagents. [ . . . ] showed no propensity toward runaway reactions. [ . . . ] and suitable for multi-kilogram scale-up” (J. Org. Chem. 2003, 23, 3695). Knochel's procedure consists of halogen-magnesium exchange. The synthesis of C6F5MgBr and other fluorinated aryl Grignards via Knochel's procedure is described in Tetrahedron Letters 1999, 40, 7449, which is incorporated herein by reference.